Trying to solve a minor issue

[KV57]

Hi
I own a 2007 Forester XT, I love it but I can be a bit OCD where my car is concerned, I am a aircraft engineer by trade and really am a bit difficult about things being right.The car has a full subaru service history with every stamp.

On medium throttle it feels like there are flat spots in the middle rev ranges, seeing as the engine has done 100k I just changed the o2 sensor and maf sensor anyway as they were not expensive and at that amount of miles I would want to have done that before I start chasing power anyway, the flat spots are still there, I pulled the plugs and whilst in perfect condition and look quite new they are Bosch FR7N133 which is the bosch plug for these engines, I note that ngk should be used and honestly I have had issues with bosch plugs on a audi before, is the Subaru picky with plugs and would I be better off fitting the ngk's?

Thanks for your help in advance

[Jay762]

Plug gap is important but as you have a flat spot not lumpy running I would have thought it was more a air / fuelling issue. Has the flat spot appeared recently?

[savage bulldogs]

Most of us run ngk 7's with a slightly smaller 0.65 mm gap in higher boost aplications (remapped )

As Jay said the air and fuelling could also cause flat spots .

When was the last time the air filter was changed and do you use the same octane fuel everytime ?

If it's not broke .....upgrade it 😊

[KV57]

3 hours ago, savage bulldogs said:

Most of us run ngk 7's with a slightly smaller 0.65 mm gap in higher boost aplications (remapped )

As Jay said the air and fuelling could also cause flat spots .

When was the last time the air filter was changed and do you use the same octane fuel everytime ?

If it's not broke .....upgrade it 😊

yeah it had a full service at 100k, all fluids and filters , new air filter, might just swap a walboro in with an external wrx filter in the bay

[KV57]

new ngk's in and flat spot gone...yay